In general, a refrigerator prevents deterioration and reduction of freshness of foods, by generating cool air by exchanging heat with cold refrigerants passing through a refrigeration cycle, and freezing or maintaining the foods at a low temperature by circulating the cool air in a freezing chamber and a refrigerating chamber. Therefore, the refrigerator stores various kinds of foods for an extended period of time.
Normally, the refrigerators are classified into direct cooling type refrigerators and indirect cooling type refrigerators. In the direct cooling type refrigerator, evaporators are installed on inner walls of a freezing chamber and a refrigerating chamber, and cool air generated around the evaporators is naturally convected to cool the freezing chamber and the refrigerating chamber. Conversely, in the indirect cooling type refrigerator, an evaporator is installed on an inner wall of a freezing chamber, a fan is installed on a cool air circulation passage, and cool air generated around the evaporator is forcibly blown by the fan to cool the freezing chamber and the refrigerating chamber.
FIG. 1 is a side-sectional view illustrating a conventional direct cooling type refrigerator.
Referring to FIG. 1, in the conventional direct cooling type refrigerator, a freezing chamber F and a refrigerating chamber R are formed in upper and lower portions of a refrigerator main body 2 having an outer casing 2a and inner casings 2b and 2c, and the front surface of the refrigerator main body 2 is opened. A freezing chamber door 4a and a refrigerating chamber door 4b are hinge-coupled to the front surface of the refrigerator main body 2 to be opened or closed. A refrigeration cycle including evaporators 10a and 10b are built in the inner walls of the inner casings 2b and 2c of the refrigerator main body 2.
The refrigeration cycle includes a compressor 6, a condenser 8, a capillary tube (not shown), and evaporators 10a and 10b, so that circulated refrigerants can be compressed, condensed, expanded and evaporated.
Here, the large parts of the evaporators 10a and 10b are closely adhered to the inner wall of the inner casing 2b of the freezing chamber F, and the other parts thereof are built in the inner wall of the inner casing 2c of the refrigerating chamber R with a predetermined gap. Temperature sensors (not shown) are built in the evaporators 10a and 10b. In a state where the evaporators 10a and 10b are built in between the outer casing 2a and the inner casings 2b and 2c, an insulation material 12 is foamed.
The conventional refrigerator includes a control unit (not shown). The control unit externally receives a set freezing temperature Tf0 and a set refrigerating temperature Tr0, receives temperature information of the evaporators 10a and 10b from the temperature sensors to form a judgment, and controls the operation of the compressor 6 according to the judgment.
On the other hand, a drain tube 14 for externally guiding condensed water formed on the inner casings 2b and 2c of the refrigerating chamber R is installed at the lower portion of the refrigerating chamber R, and a drain fan 16 for collecting the condensed water flowing through the drain tube 14 is built in the lower portion of the refrigerating chamber R.
The operation of the conventional refrigerator will now be explained. The operation of the compressor 6 is controlled according to the set freezing temperature Tf0 and the set refrigerating temperature Tr0 inputted from the control unit. As the compressor 6 is operated, the refrigerants are compressed, condensed, expanded and evaporated by the compressor 6, the condenser 8, the capillary tube and the evaporators 10a and 10b. Low temperature low pressure liquid refrigerants passing through the evaporators 10a and 10b exchange heat with air in the freezing chamber F and the refrigerating chamber R, to generate cool air. The cool air is naturally convected in the freezing chamber F and the refrigerating chamber R to maintain a low temperature.
While the refrigerating chamber R maintains a relatively higher inside temperature than the freezing chamber F, since the evaporator 10b is built in the inner wall of the inner casing 2c of the refrigerating chamber R, frost is generated on the surface of the inner casing 2c of the refrigerating chamber R.
When a defrosting operation for stopping the compressor 6 to remove the frost is performed, the frost is molten, runs down the surface of the inner casing 2c of the refrigerating chamber R, and is discharged to the drain fan 16 through the drain tube 14.
The conventional direct cooling type refrigerator reduces heat exchange efficiency due to the frost formed at the refrigerating chamber R. In addition, the frost formed at the refrigerating chamber R is molten to increase humidity, and the condensed water insanitarily contacts foods inside the refrigerator.
The cool air is only naturally convected in the freezing chamber F and the refrigerating chamber R of the conventional direct cooling type refrigerator. As a result, a large capacity refrigerator cannot be manufactured.